Tire pressure decrease detection apparatus, method, and computer readable medium therefor

Abstract

An apparatus for detecting a decrease in tire pressure based on a resonance frequency of a tire installed in a vehicle includes rotation information detection means for detecting rotation information of the tire, resonance frequency estimate means for estimating the resonance frequency of the tire from the rotation information of the tire, and judgment means for judging the decrease in the tire pressure by comparison between the resonance frequency estimated by the resonance frequency estimate means and a reference frequency preliminarily determined by learning at the time of initialization. An effective speed region when the reference frequency is determined at the time of the initialization is a first speed or less. The apparatus further includes effective speed region change means for extending an upper limit of the effective speed region to a second speed which is larger than the first speed at the time of shifting.

What is claimed is: 
     
       1. An apparatus for detecting a decrease in tire pressure based on a resonance frequency of a tire installed in a vehicle, comprising:
 rotation information detection means for detecting rotation information of the tire, 
 resonance frequency estimate means for estimating the resonance frequency of the tire from the rotation information of the tire, and 
 judgment means for judging the decrease in the tire pressure by comparison between the resonance frequency estimated by the resonance frequency estimate means and a reference frequency preliminarily determined by learning at the time of initialization, 
 wherein an effective speed region when the reference frequency is determined at the time of the initialization is a first speed and less, the first speed being the upper limit of the effective speed region, and 
 wherein the apparatus further comprises effective speed region change means for extending the upper limit of the effective speed region from the first speed to a second speed which is larger than the first speed at the time of shifting to judgment of the decrease in the pressure after learning of the reference frequency is completed. 
 
     
     
       2. The apparatus according to  claim 1 , wherein the first speed is 100 km/h and the second speed is 130 km/h. 
     
     
       3. The apparatus according to  claim 1 , wherein the number of required data of the rotation information of the tire used at the time of estimating the resonance frequency in the effective speed region whose upper limit is extended to the second speed is set to be more than the number of required data used at the time of estimating the resonance frequency in the effective speed region whose upper limit is the first speed. 
     
     
       4. The apparatus according to  claim 2 , wherein the number of required data of the rotation information of the tire used at the time of estimating the resonance frequency in the effective speed region whose upper limit is extended to the second speed is set to be more than the number of required data used at the time of estimating the resonance frequency in the effective speed region whose upper limit is the first speed. 
     
     
       5. A method for detecting a decrease in tire pressure based on a resonance frequency of a tire installed in a vehicle, including:
 a rotation information detection step for detecting rotation information of the tire, 
 a resonance frequency estimate step for estimating the resonance frequency of the tire from the rotation information of the tire, and 
 a judgment step for judging the decrease in the tire pressure by comparison between the resonance frequency estimated in the resonance frequency estimate step and a reference frequency preliminarily determined by learning at the time of initialization, 
 wherein an effective speed region when the reference frequency is determined at the time of the initialization is a first speed and less, the first speed being the upper limit of the effective speed region, and 
 wherein the method further includes an effective speed region change step for extending the upper limit of the effective speed region from the first speed to a second speed which is larger than the first speed at the time of shifting to judgment of the decrease in the pressure after learning of the reference frequency is completed. 
 
     
     
       6. The method according to  claim 5 , wherein the first speed is 100 km/h and the second speed is 130 km/h. 
     
     
       7. The method according to  claim 5 , wherein the number of required data of the rotation information of the tire used at the time of estimating the resonance frequency in the effective speed region whose upper limit is extended to the second speed is set to be more than the number of required data used at the time of estimating the resonance frequency in the effective speed region whose upper limit is the first speed. 
     
     
       8. The method according to  claim 6 , wherein the number of required data of the rotation information of the tire used at the time of estimating the resonance frequency in the effective speed region whose upper limit is extended to the second speed is set to be more than the number of required data used at the time of estimating the resonance frequency in the effective speed region whose upper limit is the first speed. 
     
     
       9. A non-transitory computer readable medium encoded with a computer program containing instructions stored therein which causes a computer, for detecting a decrease in tire pressure based on a resonance frequency of a tire installed in a vehicle, to function as
 resonance frequency estimate means for estimating the resonance frequency of the tire from rotation information obtained by rotation information detection means for detecting the rotation information of the tire, and 
 judgment means for judging the decrease in the tire pressure by comparison between the resonance frequency estimated by the resonance frequency estimate means and a reference frequency preliminarily determined by learning at the time of initialization, 
 wherein an effective speed region when the reference frequency is determined at the time of the initialization is a first speed and less, the first speed being the upper limit of the effective speed region, and 
 wherein the program further causes the computer to function as effective speed region change means for extending the upper limit of the effective speed region from the first speed to a second speed which is larger than the first speed at the time of shifting to judgment of the decrease in the pressure after learning of the reference frequency is completed.